Suction dredger with swell compensation

ABSTRACT

The tension load on the cable suspending the nozzle and conduit of a suction dredger is reduced by employing one or more reversing sheaves at the nozzle with multiple cable passes thereover. In order to &#39;&#39;&#39;&#39;sling&#39;&#39;&#39;&#39; the nozzle end pulleys or sheaves and avoid movement between the slinging cable portions and the nozzle end pulleys as swell compensation is effected, the slinging pairs of cable portions are guided and maintained sideby-side and are acted upon in unison by the swell compensation device.

D United States Patent 1 91 1111 3,893,249 Wolters 1 July 8, 1975 [54] SUCTION DREDGER WITH SWELL 3,388,070 6/1968 Born et a1 254/189 X 3,512,281 /1970 Hadjidakis.... 37/58 COMPENSATION 3,530,998 9/1970 Sprengel 254/189 X ['76] Inventor: Tjako Aaldrik lters, 3,681,862 8/1972 DeKoning et aL... 37/58 Kastanjelaan, Vianen, Netherlands 3,734,564 5/1973 McKay et a1. 254/172 X Filed: J 1974 3,739,503 6/1973 Barker et a1 37/72 X FOREl N P TENTS APPL Tl NS [21] Appl. No.: 437,761 G A OR 0 727,201 /1942 Germany 254/188 709,509 5/1931 France 37/58 Foreign Application Priority Data Feb. 2, 1973 Netherlands 73.01503 Prim ry Ex miner-Clifford D. Crowder Attorney, Agent, or Firm-John P. Snyder [52] US. Cl. 37/58; 37/72; /5;

254/172; 254/189 [57] ABSTRACT [51] Int. Cl E02! 3/90 Field 0 Search 37/58, The tenslon load on the cable suspending the nozzle 254 183 172 212/59 R 59 66 175/5 and condult of a suction dredger is reduced by emf 6 ploying one or more reversing sheaves at the nozzle with multiple cable passes thereover. ln order to sling" the nozzle end pulleys or sheaves and avoid [56] References cued movement between the slinging cable portions and the UNITED STATES PATENTS nozzle end pulleys as swell compensation is effected, 318,859 5/1885 Bowers 37/72 X the slinging pairs of cable portions are guided and 2,984,455 5/1961 Fischer 254/ R X maintained side-by-side and are acted upon in unison Prud'HOmme et 3| X the swell compensation device 3,343,810 9/1967 Parnell 254/172 3,352,540 11/1967 Schlechter 254/185 R 12 Claims, 2 Drawing Figures SUCTION DREDGER WITH SWELL COMPENSATION The invention relates to an earth dredger comprising a vessel to be anchored during dredging of earth from an underwater soil and a duct suspended by at least one cable to the vessel and having a nozzle to be inserted into the soil, a plurality of cable portions extending between lower reversing discs anchored to the duct and upper reversing discs anchored to the vessel, whilst through a swell compensator comprising a cable-length varying device the cable is connected with a winch arranged on the vessel.

This known earth dredger has the disadvantage that each long, often thick and heavy lifting cable having to position part of the duct under water moves during each movement of the vessel due to the waves along the reversing discs so that this expensive lifting cable is exposed to rapid wear particularly at the immersed lower reversing discs. When the lifting cable is replaced, the operations of the earth dredger stagnate. The cablelength varying device arranged in the known earth dredger between the winch and the upper reversing discs has a long stroke in order to compensate for high swell. In this respect the invention provides an improvement in the earth dredger of the kind set forth in the preamble by arranging said plurality of cable portions via a cable-length varying device and via guide discs held by the vessel between the lower and upper reversing discs. During the wash of the waves the cable is practically not displaced with respect to the lower reversing discs owing to said arrangement of the cablelength varying device. Moreover, the stroke of the cable-length varying device is materially shortened.

When the two ends of the cable are wound on a winch drum, the cable has a minimum shift in place during the change of position of the duct.

The invention will be set out hereinafter with reference to the drawing.

The drawings show schematically:

FIG. I an earth dredger in accordance with the invention and FIG. 2 a plan view of an exploded view of the hoisting device of FIG. I.

The earth dredger 20 shown in FIG. 1 comprises a vessel 1, which is anchored by means of anchor cables 2I during dredging of earth, for example, sand, from a soil 9. The earth dredger 20 comprises furthermore a flexible duct 3 mainly consisting of a hose accommodating a pump 5 immersed under the water level 18 and a pump 22 arranged in the vessel 1. The duct 3 has a nozzle 6 to be inserted into the soil 9 and connected by a bridge piece 23 with an outlet 8 of a pump 7 pumping the water 18 into the soil 9. The nozzle 6 of the duct 3 is suspended to the vessel I by means of a cable 10, six portions 80 of which extend, in accordance with the invention, via a cable-length varying device 26 and via six vessel-supported guide discs I5 between two upper reversing discs 14 anchored to the vessel I and three lower reversing discs 13 anchored to the duct 3. The upper reversing discs I4 are journalled in bearings 25 rigidly secured to the vessel 1, whereas the lower reversing discs 13 are journalled in a block 24, which is connected by means of cables 81 with the bridge piece 23. A swell compensator comprises a cable-length varying device formed by a hydraulic cylinder 27,

which communicates through a duct 28 with an air container 30 filled with a liquid 29 and air 31 to an extent such that the upward pressure exerted on the piston 32 is sufficient to absorb the force in the cable I0. The portions of the cable I0 extend each along two guide discs 33 and I2 rotatably journalled in bearings 17 rigidly secured to the vessel I and along one movable guide disc 34 rotatably journalled on the piston 32. The two ends of the cable I0 not passed along the upper reversing discs 14 are wound on two ganged winch drums 11 arranged on the vessel 1 and driven via a driving gear 2 by an engine 4.

When the nozzle 6 is rigidly held in the soil 9, each portion 80 of the cable 10 maintains approximately the same position relative to the winch drums I I, the upper reversing discs I4 and the lower reversing discs 13 and the guide discs 12, but the cable I0 will shift its position with respect to its guide discs I5, 33 and 34, whereas the piston 32 finds a position such that the cable 10 remains taut and the vessel I can follow the motion of the waves whilst the nozzle 6 substantially remains at its place. When the nozzle 6 is displaced for the suction process, the winch II is veered out so that the suction nozzle 19 of the nozzle 6 shifts to a greater depth in the soil 9. In order to compensate for the motion of the waves the piston 32 moves against the air enclosed in the air vessel 30 so that the swell compensator I6 releases the cable 10 or takes up the same, whilst each lower reversing disc 13 can substantially remain stationary with respect to the cable 10. It should be noted that the lifting cable 10 may have a plurality of portions differing from six.

In order to compensate for a movement of the waves producing a displacement of the guide discs 15 equal to S, the cable-length varying device 16 requires a displacement of not more than I/2S.

Instead of being formed by a hose the duct 3 may consist of three rigid tube portions pivotally connected with each other, each of which is positioned by a cable 10 in accordance with the invention.

What is claimed is:

I. In a suction dredger system comprising a buoyant vessel, and a suction dredger mounted on said vessel and including an elongate suction conduit terminating in a suction nozzle, the combination of:

a cable suspension system for suspending said nozzle from said vessel while the suction nozzle is inserted in the bottom below the vessel, said cable suspension system including at least one winch on said vessel, a cable wound on said winch and issuing therefrom, a reversing pulley connected to said suction nozzle whereby such reversing pulley is subject to an environment which is inherently dirty during dredging operation, said cable being trained over said reversing pulley and secured to said vessel whereby to present at least two cable portions extending from said vessel to said reversing pulley, guide pulley means carried by said vessel and over which said cable portions are trained to suspend said suction nozzle, further guide pulley means on said vessel for guiding and maintaining said cable portions in side-by-side relation; and

swell compensation means, engaging said cable portions which are maintained in side-by-side relation by said further guide pulley means, for paying out and taking in said cable portions in unison as said vessel rises and falls due to wave action, whereby to move said cable relative to said guide pulley means only while obviating any significant movement of the cable over said reversing pulley.

2. In a suction dredger system as defined in claim 1 including at least two reversing pulleys at said suction nozzle and a further reversing pulley on said vessel, said cable passing over one of said reversing pulleys at said suction nozzle back to and over said further reversing pulley and then back to and over the other reversing pulley at said suction nozzle and thence back to said vessel whereby to define two pairs of cable portions between the suction nozzle and the vessel, said further guide pulley means guiding and maintaining said two pairs of cable portions in side-by-side relation, and said swell compensating means engaging said two pairs of cable portions for paying them out and taking them in in unison as the vessel rises and falls.

3. In a suction dredger system as defined in claim 2 including a third reversing pulley on said nozzle and a second reversing pulley on said vessel, over both of which said cable is passed to form three pairs of cable portions all of which are engaged by said swell compensation means for movement in unison thereby.

4. In a suction dredger system as defined in claim 1 wherein said further guide pulley means comprises two sets of pulleys, one on either side of said swell compensation means.

5. ln a suction dredger system as defined in claim 4 including at least two reversing pulleys at said suction nozzle and a further reversing pulley on said vessel, said cable passing over one of said reversing pulleys at said suction nozzle back to and over said further reversing pulley and then back to and over the other reversing pulley at said suction nozzle and thence back to said vessel whereby to define two pairs of cable portions between the suction nozzle and the vessel. said further guide pulley means guiding and maintaining said two pairs of cable portions in side-by-side relation, and said swell compensating means engaging said two pairs of cable portions for paying them out and taking them in in unison as the vessel rises and falls.

6. In a suction dredger system as defined in claim 5 including a third reversing pulley on said nozzle and a second reversing pulley on said vessel, over both of which said cable is passed to form three pairs of cable portions all of which are engaged by said swell compensation means for movement in unison thereby.

7. In a suction dredger system as defined in claim 1 including a second winch on said vessel with which said cable is engaged.

8. In a suction dredger system as defined in claim 7 wherein said further guide pulley means comprises two sets of pulleys, one on either side of said swell compen sation means.

9. In a suction dredger system as defined in claim 8 including at least two reversing pulleys at said suction nozzle and a further reversing pulley on said vessel, said cable passing over one of said reversing pulleys at said suction nozzle back to and over said further reversing pulley and then back to and over the other reversing pulley at said suction nozzle and thence back to said vessel whereby to define two pairs of cable portions between the suction nozzle and the vessel. said further guide pulley means guiding and maintaining said two pairs of cable portions in side-by-side relation, and said swell compensating means engaging said two pairs of cable portions for paying them out and taking them in in unison as the vessel rises and falls.

10. In a suction dredger system as defined in claim 9 including a third reversing pulley on said nozzle and a second reversing pulley on said vessel, over both of which said cable is passed to form three pairs of cable portions all of which are engaged by said swell compensation means for movement in unison thereby.

11. In a suction dredger system as defined in claim 7 including at least two reversing pulleys at said suction nozzle and a further reversing pulley on said vessel, said cable passing over one of said reversing pulleys at said suction nozzle back to and over said further reversing pulley and then back to and over the other reversing pulley at said suction nozzle and thence back to said vessel whereby to define two pairs of cable portions between the suction nozzle and the vessel, said further guide pulley means guiding and maintaining said two pairs of cable portions in side-by-side relation, and said swell compensating means engaging said two pairs of cable portions for paying them out and taking them in in unison as the vessel rises and falls.

12. In a suction dredger system as defined in claim ll including a third reversing pulley on said nozzle and a second reversing pulley on said vessel, over both of which said cable is passed to form three pairs of cable portions all of which are engaged by said swell compensation means for movement in unison thereby. 

1. In a suction dredger system comprising a buoyant vessel, and a suction dredger mounted on said vessel and including an elongate suction conduit terminating in a suction nozzle, the combination of: a cable suspension system for suspending said nozzle from said vessel while the suction nozzle is inserted in the bottom below the vessel, said cable suspension system including at least one winch on said vessel, a cable wound on said winch and issuing therefrom, a reversing pulley connected to said suction nozzle whereby such reversing pulley is subject to an environment which is inherently dirty during dredging operation, said cable being trained over said reversing pulley and secured to said vessel whereby to present at least two cable portions extending from said vessel to said reversing pulley, guide pulley means carried by said vessel and over which said cable portions are trained to suspend said suction nozzle, further guide pulley means on said vessel for guiding and maintaining said cable portions in side-by-side relation; and swell compensation means, engaging said cable portions which are maintained in side-by-side relation by said further guide pulley means, for paying out and taking in said cable Portions in unison as said vessel rises and falls due to wave action, whereby to move said cable relative to said guide pulley means only while obviating any significant movement of the cable over said reversing pulley.
 2. In a suction dredger system as defined in claim 1 including at least two reversing pulleys at said suction nozzle and a further reversing pulley on said vessel, said cable passing over one of said reversing pulleys at said suction nozzle back to and over said further reversing pulley and then back to and over the other reversing pulley at said suction nozzle and thence back to said vessel whereby to define two pairs of cable portions between the suction nozzle and the vessel, said further guide pulley means guiding and maintaining said two pairs of cable portions in side-by-side relation, and said swell compensating means engaging said two pairs of cable portions for paying them out and taking them in in unison as the vessel rises and falls.
 3. In a suction dredger system as defined in claim 2 including a third reversing pulley on said nozzle and a second reversing pulley on said vessel, over both of which said cable is passed to form three pairs of cable portions all of which are engaged by said swell compensation means for movement in unison thereby.
 4. In a suction dredger system as defined in claim 1 wherein said further guide pulley means comprises two sets of pulleys, one on either side of said swell compensation means.
 5. In a suction dredger system as defined in claim 4 including at least two reversing pulleys at said suction nozzle and a further reversing pulley on said vessel, said cable passing over one of said reversing pulleys at said suction nozzle back to and over said further reversing pulley and then back to and over the other reversing pulley at said suction nozzle and thence back to said vessel whereby to define two pairs of cable portions between the suction nozzle and the vessel, said further guide pulley means guiding and maintaining said two pairs of cable portions in side-by-side relation, and said swell compensating means engaging said two pairs of cable portions for paying them out and taking them in in unison as the vessel rises and falls.
 6. In a suction dredger system as defined in claim 5 including a third reversing pulley on said nozzle and a second reversing pulley on said vessel, over both of which said cable is passed to form three pairs of cable portions all of which are engaged by said swell compensation means for movement in unison thereby.
 7. In a suction dredger system as defined in claim 1 including a second winch on said vessel with which said cable is engaged.
 8. In a suction dredger system as defined in claim 7 wherein said further guide pulley means comprises two sets of pulleys, one on either side of said swell compensation means.
 9. In a suction dredger system as defined in claim 8 including at least two reversing pulleys at said suction nozzle and a further reversing pulley on said vessel, said cable passing over one of said reversing pulleys at said suction nozzle back to and over said further reversing pulley and then back to and over the other reversing pulley at said suction nozzle and thence back to said vessel whereby to define two pairs of cable portions between the suction nozzle and the vessel, said further guide pulley means guiding and maintaining said two pairs of cable portions in side-by-side relation, and said swell compensating means engaging said two pairs of cable portions for paying them out and taking them in in unison as the vessel rises and falls.
 10. In a suction dredger system as defined in claim 9 including a third reversing pulley on said nozzle and a second reversing pulley on said vessel, over both of which said cable is passed to form three pairs of cable portions all of which are engaged by said swell compensation means for movement in unison thereby.
 11. In a suction dredger system as defined in claim 7 including at least two reversing pulleys at said suction nozzle and a further reversing pulley on said vessel, said cable passing over one of said reversing pulleys at said suction nozzle back to and over said further reversing pulley and then back to and over the other reversing pulley at said suction nozzle and thence back to said vessel whereby to define two pairs of cable portions between the suction nozzle and the vessel, said further guide pulley means guiding and maintaining said two pairs of cable portions in side-by-side relation, and said swell compensating means engaging said two pairs of cable portions for paying them out and taking them in in unison as the vessel rises and falls.
 12. In a suction dredger system as defined in claim 11 including a third reversing pulley on said nozzle and a second reversing pulley on said vessel, over both of which said cable is passed to form three pairs of cable portions all of which are engaged by said swell compensation means for movement in unison thereby. 